This invention is generally directed to humidity detectors comprised of ladder polymers. More specifically, the present invention is directed to ultrasensitive relative humidity detectors, or humidity sensors comprised of a ladder polymer or ladder polymers, and which detectors can be selected for electrostatic imaging and printing apparatuses. Also, the humidity sensors or detectors of the present invention can be incorporated in feedback, such as known feedback control circuit and control systems. In embodiments, the humidity detectors of the present invention have a dc dark conductivity of 5.times.10.sup.-14 (ohm-cm).sup.-1 which increases by more than about three orders of magnitude to 5.times.10-10.sup.-1 (ohm-cm).sup.-1 when the relative humidity in air increases to, for example, 50 percent. The humidity can be measured by a number of known methods, such as by utilizing a humidity detector, like the VAISALA Model HM132, and the dark conductivity can be measured by utilizing, for example, an electrometer, like the electrometer model Keithley 617. With the sensors of the present invention, relative humidities of from, for example, zero to about 95 percent can be measured in embodiments to provide feedback information for adjusting corona charging currents in imaging and printing systems, such as reprographic and electrostatic imaging systems. Also, in embodiments the detectors, or sensors of the present invention can be utilized to adjust and control the developer composition bias voltage in, for example, imaging and printing systems, and to maintain excellent developed image copy quality independent of environmental humidity.
Ladder polymers that can be selected for the invention of the present application are illustrated in U.S. Pat. No. 5,248,580, the disclosure of which is totally incorporated herein by reference. More specifically, there is illustrated in this copending patent application photoconductive imaging members with a photoconductive ladder compound, such as an imidazoquinoline ladder polymer like poly(7-oxo-7,10H-benz[de]-imidazo(4',5':5,6) benzimidazo[2,1-a]isoquinoline-3,4:10,11-tetrayl)-10-carbonyl), which polymers may be a cis-, trans- or mixture of cis- and trans-isomers referred to as BBL or poly(benzimidazole-benzophenanthroline)-type ladder and closely structurally related benzimidazole-benzophenanthroline-type semi-ladder polymer referred to as BBB which polymers may be a cis-, trans- or mixture of cis- and trans-isomers. Examples of ladder polymers that may be selected as the photogenerating pigments for the imaging members of the copending application include those of formulas illustrated in FIGS. 2 through 7 representing the representative structures of BBL, BBB, BBL-N, BBL-P, BBL-DBF and BBL-AQ, respectively, where the subscript n is an integer representing the number of segments, and the value of which in embodiments is greater than about 10, and is in the range of from about 10 to about 1,000.